1. Field of the Invention
The present invention relates to a peripheral LSI in an embedded system of a cellular phone, digital still camera or the like. Here, a peripheral LSI refers to a semiconductor integrated circuit which helps processing by a CPU core.
2. Description of Related Art
In recent years, a semiconductor device called a multi-chip module or system-in-package which combines a CPU core chip and a peripheral LSI chip has been increasingly used. Usually a peripheral LSI in this type of semiconductor device starts operation according to a start instruction which it receives from the CPU core.
The peripheral LSI should transfer data between the CPU core and a peripheral device. As stated on pp.580-609 of “LOGIC AND COMPUTER DESIGN FUNDAMENTALS,” M. MORRIS MANO, 2000, PRENTICE HALL, there are three data transfer methods which are used in such circumstances.
The first data transfer method is used in a situation which involves processing of large volumes of data as in video encoding. In this method, the peripheral LSI serves as a bus master for data transfer. The second data transfer method uses the CPU core as a bus master. In the third method, a DMAC (direct memory access controller) connected with the CPU bus serves as a bus master for data transfer. In all these three methods, the whole semiconductor device including the peripheral LSI makes up one CPU core memory space.